The present disclosure relates to devices, systems and methods for approximating tissue. More particularly, it relates to endovascular, percutaneous or minimally invasive devices, systems and methods for approximating tissue at various anatomical regions, for example in repairing a cardiac valve (such as the mitral valve) via leaflet edge-to-edge approximation or attachment.
The heart is a four-chambered pump that moves blood efficiently through the vascular system. Blood enters the heart through the vena cava and flows into the right atrium. From the right atrium, blood flows through the tricuspid valve and into the right ventricle, which then contracts and forces blood through the pulmonic valve and into the lungs. Oxygenated blood returns from the lungs and enters the heart through the left atrium and passes through the mitral valve and into the left ventricle. The left ventricle contracts and pumps blood through the aortic valve, into the aorta, and to the vascular system.
The mitral valve consists of two leaflets (anterior and posterior) attached to a fibrous ring or annulus. The leaflets each form a free edge opposite the annulus. The free edges of the leaflets are secured to lower portions of the left ventricle through chordae tendineae (or “chordae”) that include a plurality of branching tendons secured over the lower surfaces of each of the valve leaflets. The chordae are further attached to papillary muscles that extend upwardly from the lower portions of the left ventricle and interventricular septum.
In a healthy heart, the free edges of the mitral valve leaflets close against one another (or coapt) during contraction of the left ventricle to prevent oxygenated blood from flowing back into the left atrium. In this way, the oxygenated blood is pumped into the aorta through the aortic valve. However, due to cardiac disease, valve defects, or other reasons, the leaflets may be caused to remain partially spaced or open during ventricular contraction (e.g., leaflet prolapse) and thus allow regurgitation of blood into the left atrium. This results in reduced ejection volume from the left ventricle, causing the left ventricle to compensate with a larger stroke volume. Eventually, the increased work load results in dilation and hypertrophy of the left ventricle, enlarging and distorting the shape of the mitral valve. Mitral valve regurgitation in an increasingly common cardiac condition that can quickly lead to heart failure, dangerous arrhythmias, and other serious complications.
It is common medical practice to treat mitral valve regurgitation by either valve replacement or repair. Valve replacement conventionally entails an open-heart surgical procedure in which the patient's mitral valve is removed and replaced with an artificial valve. This is a complex, invasive surgical procedure with the potential for many complications and a long recovery.
Mitral valve repair includes a variety of procedures to repair or reshape the leaflets and/or the annulus to improve closure of the valve during ventricular contraction. If the mitral valve annulus has become distended, a frequent repair procedure involves implanting an annuloplasty ring or band on the mitral valve annulus. Another approach for treating mitral valve regurgitation requires a flexible elongated device that is inserted into the coronary sinus and adapts to the shape of the coronary sinus. The device then undergoes a change that causes it to assume a reduced radius of curvature, and as a result, causes the radius of curvature of the coronary sinus and the circumference of the mitral annulus to be reduced. A more recent technique for mitral valve repair entails the suturing or fastening or approximating of segments of the opposed valve leaflet free edges together, and is referred to as a “bow-tie” or “edge-to-edge” technique. While all of these techniques can be very effective, they usually rely on open heart surgery where the patient's chest is opened, typically via sternotomy, and the patient placed on cardiopulmonary bypass. While some percutaneous or transcatheter mitral valve repair procedures have been contemplated premised upon the edge-to-edge technique, the confined nature of the native mitral valve anatomy renders capturing and securing of the leaflets with a single clip or device exceedingly difficult. Capturing a first leaflet may be relatively straightforward, but then the anchor on that leaflet constrains grabbing the other leaflet.
Procedures at other valves and other anatomical regions also seek to achieve tissue approximation on a minimally invasive basis, and are faced with many of the same obstacles described above with respect to the mitral valve.
In light of the above, a need exists for devices, systems and methods for minimally invasive tissue approximation at various anatomical regions such as in repairing a mitral valve in the treatment of mitral valve regurgitation.